U.S. Pat. No. 5,076,344 for example discloses a process in which a molten standard aluminum alloy is fed to a casting or fill chamber through a suction tube. From there, the molten aluminum alloy is then charged into the casting chamber and into the evacuated chamber of a mould, by means of a piston. Inside said mould chamber, the concentration of the parting compound, an alkali halide, is 0.5 to 3% by weight, whereas in the casting chamber the concentration of this parting compound which simultaneously acts as a lubricant here, is between 2 to 7% by weight. The parting compound preferred in this process is an aqueous solution of potassium iodide. The parting compound which is applied to the mould and the plunger prevents the aluminum alloy from sticking to the walls of the mould chamber or the plunger piston, resp. and the casting chamber. The parting compound thus contributes to a continuous and smooth flow of the process.
The disadvantage involved in the use of alkali halides, particularly potassium iodide, is that this salt will corrode the steel-containing parts of the apparatus performing said process. Moreover, the feed process, which is effected via a suction tube, is awkward. Another problem associated with this prior art process is that the quality of the diecastings is impaired by gas inclusions as well as other impurities. The corrosion of the steel can lead to impurities in the metal alloy since corroded bits and particles may come off the steel surface.
Furthermore, the known processes are often complex, thus requiring a machine of likewise complex construction which in turn results in high maintenance costs--all of which makes these processes uneconomic.
Meanwhile, the industries further processing such light metal parts have come to expect additionally improved material properties such as higher strength, lower weights, thin walls, complex geometries, capability of being further processed such as weldability, heat treatability or the possibility of using modern connection technologies when assembling or installing and disassembling or removing such parts.